Hey Danny, I don't use saw tooth hangers, I hate them! Instead, I use triangle shaped hangers. When the material used is too thin for screws or nails, I use the E6000. For a larger plaque, I'll use two of the hangers. I use a dab of E6000, enough for it to squeeze through the screw hole in the hanger. You definitely need to give it more than an hour though. I let it set over night. Have never had a failier.
Another thing you can do is glue and clamp a thicker cleat to thetop, back of the backer board. Then you can mount what ever you want.